GMAG Student Dissertation Award: When conductivity and magnetism emerge at a spinel/perovskite heterointerface

The plethora of fascinating properties observed in oxide heterostructures has attracted a lot of interest. Most noticeably, the confined electron gas formed at the interface between the two insulators LaAlO₃ and SrTiO₃ features e.g. gate-tunable superconductivity, ferromagnetism and non-volatile memory effects. Numerous studies have been devoted to understand the origin of the conductivity along with enhancing its properties, in particular the electron mobility. Recently, we found¹ that substituting perovskite LaAlO₃ with spinel γ-Al₂O₃ can produce a confined electron gas with a record-high electron mobility exceeding 140,000 cm²/Vs. Here, we show that the γ-Al₂O₃/SrTiO₃ interface conductivity originates from oxygen vacancies and use defect engineering to control various interface properties². In addition, we reproduce the high mobility and show that it coexists with a strain-tunable magnetic order below 40 K and a positive, non-saturating magnetoresistance of up to 80,000% at 15 T. The study evidences that the γ-Al₂O₃/SrTiO₃ heterostructure paves the way for combining lattice, spin and electronic degrees of freedom.